With the change to ASCE 7-10, the uplift calcs are not that much more, and in some cases less, but I think in any case the concern is wind-borne debris. If the mod stays attached to the roof, we are good. Having lived through it, it's all theory anyway. In a hurricane, theory goes out the window.
Jason Szumlanski Fafco Solar On Mar 24, 2012, at 6:16 PM, Kent Osterberg <k...@coveoregon.com> wrote: > Many inland areas in California, Oregon, and Washington are 85 mph zones. I > think that's the lowest requirement anywhere in the U.S. I can't imagine > designing for 185 mph winds. > Doesn't that just blow the glass out of the modules? > > Kent Osterberg > Blue Mountain Solar, Inc. > www.bluemountainsolar.com > > > On 3/24/2012 2:07 PM, Jason Szumlanski wrote: >> Oh, to have 85 mph winds. Code changes just brought us up to 180 mph >> design wind speeds in Southwest Florida. Yay. >> >> Jason Szumlanski >> Fafco Solar >> >> On Mar 24, 2012, at 5:05 PM, Kent Osterberg<k...@coveoregon.com> wrote: >> >>> William, >>> >>> There are auger mounted systems that don't require any concrete. For >>> locations with suitable soil, they probably save some time and are a little >>> less expensive than concrete. But it takes a substantial structure to >>> withstand 85 mph, or greater, winds. There's no getting around the physics >>> of that. >>> >>> Oregon also requires PV mounting structures to be engineered unless they >>> meet conditions prescribed in the solar installation code. The prescriptive >>> rules only apply to roof mounted systems, so ground mounts require a >>> structural engineer to sign off on the construction plans. >>> >>> Kent Osterberg >>> Blue Mountain Solar, Inc. >>> www.bluemountainsolar.com >>> >>> >>> On 3/24/2012 10:29 AM, William Miller wrote: >>>> Daryl: >>>> >>>> Thanks for the photos and description of the mounts you are installing. >>>> We have installed many of the DPW ground mount systems in similar >>>> configurations. >>>> http://millersolar.com/MillerSolar/Portfolio/ground-mount/engineered_ground_mount.jpg >>>> >>>> We are realizing two things: >>>> >>>> 1. Concrete footings of any type are expensive. The cost of excavation, >>>> forming and concrete really adds up. >>>> >>>> 2. For off-grid, when the module tilt angle increases to 45 degrees, the >>>> foundations need to be substantial. During one install we had our heavy >>>> PV trailer blow over due to high winds. We decided to have the >>>> foundations reviewed by an engineer and when we received the results, we >>>> had to go back and double our piers and strut. We had bid the job so the >>>> updates came out of our pocket. See: >>>> http://millersolar.com/MillerSolar/Portfolio/ground-mount/full_size_photos/engineered_ground_mount.JPG >>>> >>>> We are now required by the AHJ to provide a wet stamp from a structural >>>> engineer for every PV structure over 6 feet in height. This means every >>>> off-grid. We know the engineers will require massive foundations which >>>> will cost a lot. I am looking for a cheaper way to install these racks. >>>> I have not found it yet. >>>> >>>> Thanks for your input. >>>> >>>> William Miller >>>> >>>> >>>> At 04:37 AM 3/24/2012, you wrote: >>>>> William, >>>>> I'm attaching a picture of a system we just completed in Eleuthera >>>>> using DPW racks on concrete pilings. We tied the pilings and rebar >>>>> reinforcement into the limestone bedrock with rebar down 16 inches and >>>>> used 12 inch sono tubes as forms. >>>>> We do a lot of ground mounting since our summer work is mostly in New >>>>> England and snow removal is always a factor. I have two pole mounted >>>>> arrays at my home, but it is the most expensive option, and therefore >>>>> do a lot of this type of ground mounting. We also have an economical >>>>> "cribworks" type structure made from solid railroad ties and weighing >>>>> in at about 2800 lbs each that we will sometimes offer to customers in >>>>> off grid situations. >>>>> >>>>> Daryl >>>> >>>> > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
